ㅋㅋㅋ, k-k-k, kekeke: leet mutation?

What’s weird about it is that the root of the expression is actually ㅋㅋㅋ, which is to say, kkk, without any vowels… and that, usually, when I catch students trying to render ㅋㅋㅋ in English writing, they use a simple “kkk” or k-k-k instead of kekeke. I have to wonder where the vowels got added in, or why this variant in any case arose among Korean gamers….